I can't seem to find the right settings for Sonic Generations because it most of the time it's kinda choppy and rough. I know for a fact that the more resolution you give a program, the more slower it gets depending on how powerful your PC is. My monitor can hold up to maximum resolution for the general computer, but setting it for the latest PC games will make it really slow.

My processor:

Intel(R) Core (TM) 2 Duo CPU E4600 @2.40GHz 2400Mhz 2 Cores 2 Logical Processors